python3-cryptography: Add legacy-openssl packageconfig

python3-cryptography: Add legacy-openssl packageconfig

Fixes [YOCTO #15416]

The OpenSSL legacy provider supplies algorithms that are either used
infrequently or have been deemed insecure by modern standards. The
Python3 cryptography module can optionally support this provider via the
openssl-ossl-module-legacy package.

Currently, the cryptography module builds with legacy provider support
enabled by default, regardless of whether the legacy modules are
actually included in the system. This patch makes that dependency
explicit by introducing a legacy-openssl packageconfig option that:

* Ensures runtime dependency on openssl-ossl-module-legacy when enabled
* Allows users to disable legacy algorithm support via build configuration
* Aligns python3-cryptography's defaults with OpenSSL's current defaults

The packageconfig option defaults to enabled for consistency with
OpenSSL's current configuration and to avoid breaking existing
deployments. A future security improvement will disable legacy modules
by default in OpenSSL, at which point this packageconfig can also
default to disabled.

Signed-off-by: Colin Pinnell McAllister <colinmca242@gmail.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>